The objective of this exploratory clinical trial is to apply Unreal Engine 5 (UE5)-based Mixed Reality (MR) technology to achieve real-time stereoscopic visualization of surgical planning, personalized free flap harvest and defect reconstruction, accurate oral cancer resection, and precise morphological and volumetric matching of the reconstructed free flap to the defect site.

Researchers adopted a parallel controlled design, with participants randomized into three groups: Experimental Group 1 (undergoing Mixed Reality [MR] technology-assisted surgery), Experimental Group 2 (undergoing virtual surgical guide-assisted surgery), and Control Group (undergoing conventional surgery). A total of 30 participants will be recruited, with 10 cases in each group.

The primary purpose is to confirm the effectiveness of MR technology in assisting oral cancer resection, free flap design, harvest, and defect reconstruction. Allocation concealment will be implemented via the sealed envelope method.

Study population: Patients with oral cancer confirmed by preoperative pathology (tumor diameter > 3 cm), who had defects suitable for free flap reconstruction, signed written informed consent, agreed to complete postoperative follow-up, and were medically eligible for major surgery. This study was conducted at the Department of Oral and Maxillofacial-Head and Neck Oncology, the Ninth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine.

The study is conducted at the Ninth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine.

Primary research questions & outcome assessments:

1. Whether UE5-based MR technology enables precise morphological and volumetric matching of free flaps in oral cancer reconstruction.
2. Comparisons of operative duration, flap characteristics (utilization, volume, survival), and primary wound healing rate between mixed reality (MR), virtual surgical guide, and conventional surgery.
3. Whether MR technology can overcome the limitations of virtual surgical guide systems and further enhance surgical efficiency and precision.

Researchers adopted a parallel controlled design, with participants randomized into three groups: Experimental Group 1 (undergoing Mixed Reality [MR] technology-assisted surgery), Experimental Group 2 (undergoing virtual surgical guide-assisted surgery), and Control Group (undergoing conventional surgery). A total of 30 participants will be recruited, with 10 cases in each group. The primary purpose is to confirm the effectiveness of MR technology in assisting oral cancer resection, free flap design, harvest, and defect reconstruction. Allocation concealment will be implemented via the sealed envelope method.

During the study period, participants will be required to complete the following main tasks and receive relevant interventions:

Preoperatively: Cooperate with computed tomography (CT) data acquisition and complete ultrasonic localization/computed tomography angiography (CTA) examinations (for flap region localization, identification of perforator positions and flap thickness, and corresponding body surface marking). Participants will also collaborate with researchers to design the tumor resection margin, as well as the shape and volume of the free flap to be harvested. After signing the informed consent form, participants will receive surgical treatment corresponding to their randomization assignment.

Intraoperatively: Following the onset of general anesthesia, participants will cooperate with routine surgical skin preparation and draping. For participants in Experimental Group 1, registration and fusion must be completed prior to the initiation of formal surgery to ensure the registration accuracy of MR technology during the operation. In accordance with the preoperative surgical plan, precise tumor resection, free flap harvest, and defect reconstruction will be performed with MR guidance.

Postoperatively: Complete follow-up visits as required, including outpatient follow-ups at 2 weeks ± 3 days, 1 month ± 7 days, 3 months ± 2 weeks, and 6 months ± 1 month postoperatively. Participants will cooperate with physical examinations, CT/magnetic resonance imaging (MRI) scans, and Likert scale assessments, and assist researchers in collecting surgery-related and postoperative recovery data. CT scans will be performed at 1 month and 6 months postoperatively; engineers will import the CT data into a computer, fuse it with the preoperative design scheme, and calculate the morphological similarity (expressed as a percentage).

During the study period, participants must promptly inform researchers if disease progression, complications, or other conditions precluding continued study participation occur. Participants may voluntarily withdraw from the study at any time without affecting their standard medical care.

Participants shall cooperate with researchers in data collection and refrain from participating in other clinical studies or related treatments that may interfere with the results of this study.

Inclusion Criteria:

1. Definite pathological diagnosis of oral cancer before surgery;
2. Defects suitable for free flap reconstruction;
3. Patients have signed the informed consent form and are willing to cooperate with postoperative follow-up.

Exclusion Criteria:

- Poor general condition, evaluated as unable to tolerate surgical treatment.

-Exclusion Criteria (After Enrollment)

Subjects who have been enrolled in this trial will be excluded if they meet any of the following conditions:

1. Violation of important inclusion criteria;
2. Subjects did not receive surgical treatment;
3. No observation data after randomization. Withdrawal Criteria Withdrawal of subjects from the trial refers to cases where enrolled subjects are determined by the investigator to withdraw from the trial due to conditions that make it inappropriate to continue the trial. In accordance with the informed consent form, subjects have the right to withdraw from the trial midway. Subjects who do not explicitly propose to withdraw but stop receiving treatment and tests and are lost to follow-up are also considered "withdrawn" (or "lost to follow-up"). The reason for withdrawal should be understood and recorded as much as possible, such as: poor subjective curative effect; inability to tolerate certain adverse reactions; inability to continue participating in the clinical study due to personal reasons; economic factors; or lost to follow-up without stating the reason.

(1) Aggravation or deterioration of the condition during the trial that requires emergency measures; (2) Occurrence of certain comorbidities, complications or special physiological changes in subjects during the trial, making it inappropriate to continue participating in the trial; (3) Voluntary withdrawal by the subject.

Data Handling of Withdrawn Subjects

Regardless of the reason, the complete clinical data of subjects who withdraw from the trial shall be retained. For all withdrawn subjects, the trial conclusion form and the reason for withdrawal shall be filled in the case report form (CRF). Generally, there are 6 types of reasons: occurrence of adverse events (including adverse drug reactions and allergic reactions), lack of efficacy (deterioration of condition or occurrence of complications), violation of the trial protocol (including poor compliance), lost to follow-up (including voluntary withdrawal by the patient), termination by the sponsor, or others.

IPD will not be shared because the study involves sensitive patient data related to head and neck cancer surgery, including clinical, imaging, and surgical outcome information that could compromise patient privacy and confidentiality if shared. Additionally, the study is still in progress, and premature sharing of IPD may compromise the integrity of the primary analysis and publication plans. Restrictions on IPD sharing are also imposed by the institutional review board (IRB) and ethical guidelines to protect the rights and welfare of study participants, as well as by the data use agreements with participating institutions.